Gas Bio-filtration is a relatively new technology used to purify contaminated air from volatile organic and inorganic compounds VOC’S and VIC’S, aromatic compounds and other toxic and odorous compounds.

Our main aim is to study use of bio filters for controlling air pollution in industries having above mentioned pollutants.

The experience gained from monitoring exercise carried out during the last 25 years and adoption of appropriate strategy for air quality control have been discussed in this paper presentation.

Introduction

Bio filtration is air pollution control technique which Involves bio degradation of contaminants under the action of microorganisms diffused in a thin layer of moisture known as “BIOFILM” ,Mainly used for elimination of malodorous gas emissions and low concentrations of Volatile Organic Compounds (VOCs).

The process of Bio Degradation is :

Organic Pollutant + O2 CO2 + H2O + Heat + Biomass

Brief Timeline Of Development Of Bio Filters

1923 – Biological methods were proposed to treat odorous emissions

1955-Biological methods were applied to treat odorous emissions in low concentrations in Germany

1960’s-Bio filtration was used for the treatment of gaseous pollutants both in Germany and US.

Air pollution Statistics

1970’s- Biofiltration is used with high success in Germany

1980’s -Biofiltration is used for the treatment of toxic emissions and volatile organic compounds (VOCs) from industry.

1990’s -Today, there are more than 500 biofilters operating both in Germany and Netherlands and it is widely spreaded in US.

SUPPORT RACK -perforated – allow air from the plenum to move into the bed media -to contact microbes that live in the bed. Perforations also permit excess, condensed moisture to drain out of the bed to the plenum.

FAN – used to collect contaminated air, As the emissions flow through the bed media, the pollutants are absorbed by moisture on the bed media.Microbes reduce pollutant concentrations by consuming and metabolizing pollutants. During the digestion process, enzymes in convert compounds into energy, CO2 and water. Material that is indigestible is left over and becomes residue.

Design and Performance Parameters

Contact Time and Air Flow

Moisture Content

Temperature

Siting

Media

Microorganism Seeding

Construction

Weeds

Rodents

Health and Safety Concerns

Costs

TEMPERATURE: Most microbes can survive and flourish in a temperature range of 60 to 105 /F (30 to 41/C) (Ref. 3 of EPA PDF). When emissions are too hot, humidifiers are used which cools gases down by evaporative cooling.

MOISTURE: Moisture creates the bio-film that removes (absorbs) pollutants from an air stream so that they can be assimilated by microbes. Humidifiers made from an old FRP (fiber reinforced plastic) tank are used to increase moisture.

CARE AND FEEDING : Microbes need a diet of balanced nutrients to survive and propagate. Pollutants provide the main source of food and energy, but microbes also require macronutrients to sustain life. Microbes use nitrogen to build cell walls. some nitrogen products form water-soluble compounds and are leached out of the system with condensing water. Nitrogen, phosphorus, potassium added by incorporating agricultural fertilizer into bed media.

ACIDITY: Most bioreactors perform best when the bed pH is near 7, or neutral. hydrogen sulfide, organic sulfur compounds, and halogens (chlorine, fluoride, bromine and iodine) are acidic in nature and lower the pH.

Oyster Shells may be added to neutralize the pH. a Dilute solution of soda ash (sodium carbonate, Na2 CO3) may be introduced by a garden hose periodically.

Design, installation and operation will impact building ventilation and bio-filters effectiveness.

Review Of Researches

In research on Transient Behavior of Biofilter , Marc A. Deshusses describes the aerobic biodegradation of VOC mixtures from effluent air streams in laboratory scale compost based biofilters. Bio filters had degraded and absorbed Hexane , Acetone , MIBK , propane and MEK in different proportions. Established a fundamental description of pollutant removal in biofilters.

Biofiltration-an Innovative Technolgy For The Future

different types of biofilters’ support media

the various biofilters operations adopted in industry.

waste compounds treatable by biofiltration

commercial potential of biofiltration.

The paper concludes that when compared to other available technologies, biofilters have significant technical and economical advantages.

A Few Existing Bio Filters

McMinnville, Oregon: The installation in McMinnville, Oregon perhaps best demonstrates the capabilities as the levels of odorous compounds to be treated were among the highest ever reported from the wastewater treatment environment.

Long Sault, Ontario: Although a small (1500 cfm), indoor, container-type system, this installation demonstrates several key aspects that are relevant to any installation.

Sarnia, Ontario: This biofilter was installed in 2001 and treats 12,500 cfm of air coming from a sludge liming and drying operation.

Brookfield, P.E.I. : This biofilter was installed in 2002, at a composting plant in P.E.I., that treats 60,000 cfm of air from the composting process.

Toronto, Ontario: This biofilter was installed in 2002 in the north end of Toronto at the Toronto Mixed Waste Recycling and Organics Processing Facility.